The present invention relates to a method of forming oxide film, and more particularly to a method of forming oxide which makes it possible to form an oxide film at low temperature.
A prior art technology about an oxide film forming method is described by using a silicon substrate.
A thermal oxidation method is well known as a method for forming an oxide film on the surface of a silicon substrate. In this method, an oxide film is formed at a high temperature, e.g. more than 600.degree. C. by bringing a silicon substrate into contact with gas such as dry oxygen, dry oxygen containing a slight amount of hydrogen chloride, or oxygen containing moisture. However, such a method cannot be applied to the low temperature process since the formation of oxide film is carried out at high temperature.
The importance of the low temperature process is described below by reference to the formation of the oxide film of MOS LSI.
A rapid advancement has been made in the LSI technology and DRAM with more than 1 Mbit has already been put into practice. In order to manufacture high efficiency electronic devices, i.e. devices with ultrafine pattern and ultrahigh integration, a high performance process which is highly controlled and not affected by various indeterminate factors is required. The low temperature process is cited as a high performance process.
For example, lowering the formation temperature of an oxide film results in decrease of the impurities released from materials constituting a reaction system. Consequently, the trap density in an oxide film and at the interface between the oxide film and silicon are reduced, and therefore an electrically stable semiconductor device can be realized.
The low temperature process is also effective to decrease the deformation of silicon substrate, and the strain and the defect density in materials constituting a semiconductor device.
Furthermore, if the formation temperature of an oxide film is lower than 600.degree. C., an oxide film can be formed even after the formation of metal or metal alloy with low melting point such as aluminum. Therefore, a semiconductor having various functions can be realized. A temperature of less than 500.degree. C. is particularly desirable since no hillock generates in an aluminum thin film.
As mentioned above, lowering the formation temperature of oxide film is inevitable to realize ultrafine patterned LSI.
The purpose of the present invention is to provide a method of forming oxide film at low temperature.